This invention relates to reciprocating piston devices, such as pressure pumps, vacuum pumps and compressors.
Single-acting pistons are typically reciprocated by a crank joined to the nonworking end of the piston by a connecting rod. However, when a piston is to be double acting, the conventional method of reciprocating the piston is not feasible.
My prior U.S. Pat. No. 3,410,477 discloses a vacuum pump employing a double-acting piston which is driven by an eccentric which is received within the piston. Similarly, my U.S. Pat. No. 3,834,840 shows a similar reciprocating piston device in which a piston is driven by an eccentric received within the piston and special planar roller bearings are provided at the opposite ends of a yoke for accommodating the lateral component of motion from the eccentric.
Although both of my prior patented reciprocating piston devices function satisfactorily, the earlier patented construction requires relatively close tolerances for the drive assembly. My later patented construction overcomes this problem but some difficulty has been experienced in keeping the planar bearings properly lubricated. The loss of lubricant accelerates wear and can bring about premature failure. Because of the heat of compression, this problem is most acute for compressors.